The present invention relates to a valve plate or control disc for an axial piston machine of the swash plate type, which in its control surface is provided with control openings and bearing pockets for hydrostatically mounting the valve plate on the rotating cylinder drum of the axial piston machine, in which the control openings communicate with the bearing pockets through throttle passages.
A valve plate of the above-described type is disclosed in the German Pat. No. 2,157,704 and the corresponding U.S. Pat. No. 3,803,984. The basic feature of the valve plate disclosed in these patents is to permit the compensation of additional forces, occurring in the gap between adjacent faces of the valve plate and the cylinder drum depending on the relative position of the two elements with each other, by means of hydrostatic bearings with in series connected throttles. In this known construction the hydrostatic thrust bearings are formed as shallow grooves arranged in pairs in circumferential direction of the valve plate with small radial distance from each other in the two dead center regions and connected by channels to annular gaps formed between pressure cylinder bores, extending from the rear face of the valve plate into the latter, and pistons respectively inserted therein. The connection between the control openings and the bearing pockets is constructed in such a manner that a bore branches off from a control opening and leads to one cylinder bore, eventually by a further bore connected to the first-mentioned one. An annular groove is provided in the cylinder bore spaced from the mouth opening of the bore. Furthermore, the piston is arranged in the cylinder bore in such a manner that the piston can perform oscillating movements. In this way it is usually possible to prevent that foreign particles will settle between the pressure piston and the cylinder in the location between the mouth of the bore and the annular groove.
A further bore leads in tangential direction from the annular groove to the periphery of the valve plate or control disc. The bore is closed at the periphery by a plug or the like. An additional bore, normal to the first-mentioned one, branches off from the latter and leads into the respective bearing pocket for maintaining a hydrostatic bearing. Four such connections are provided in the known valve plate.